OPTICAL WAVEGUIDE MODULE

PROBLEM TO BE SOLVED: To prevent a clad mode generated within a laser diode (LD)-optical waveguide coupling part and an optical waveguide element from leakage into optical fibers facing this LD by forming grooves of the direction crossing the optical waveguides on both sides of the optical waveguides and applying light shieldable films on the inside walls of these grooves. SOLUTION: The light of a wavelength (λ2) of 1.3μm emitted from the LD is guided through an LD port 19, a branching part 12b and a filter 13 to a common port 14. At this time, the clad mode is generated in the coupling part of the LD and the optical waveguides 11, the branching part 12a and the branching part 12b of the yshaped waveguides. This clad mode is confined and propagated between a substrate 10 and the air layer in the upper part of the clad layer 21, is reflected and absorbed by the grooves 28 formed with the metallic films 30 and is shut off by a groove side bench 29. The leaking of the clad mode from the LD into the optical fibers 18 of the reflection port 17 is, therefore, suppressed.